A rotary gantry of a CT machine is installed with several components, thus the equilibrium of mass distribution should be taken into consideration in the mechanical design, to ensure that the rotary gantry of the CT machine may rotate evenly, thereby obtaining high-quality images.
Reference is made to FIG. 1, which is a schematic view showing an assembling structure of a CT gantry according to an embodiment in the conventional technology.
In practice, errors of various components in the mechanical manufacture and installation processes cause the imbalance of mass distribution of the gantry, that is, a centre of mass M of the gantry deviates from a rotation center, and as shown in FIG. 1, such eccentricity may generate a resultant force Fr at the centre of mass M.
Fr may be decomposed into a force Fd in a diametrical direction and a force Ft in a tangential direction. The periodic variation of Fr will cause the periodic variation of both of the two force components, and the periodic variation of the force component Ft will apply a periodic moment on the gantry during the rotation of the gantry, and in this case, the rotation velocity of the gantry is nonuniform. The image quality will be affected when the force Fr reaches a certain value, and the vibration caused by the force Fr may adversely affect the service life of a bearing. Therefore, a weight counterbalancing position is required to be arranged on the gantry, and counter weight at the weight counterbalancing position is adjusted to locate the centre of mass of the rotary part of the gantry at the rotation center of the gantry to the greatest extent, so as to reduce the influence caused by the deviation of the centre of mass.
In view of the above issues, in a Chinese patent No. 200410071323.6 titled “SYSTEM AND METHOD FOR BALANCING CT GANTRY”, imbalance information is collected by a specific sensor so as to perform weight counterbalance properly. In a Chinese patent No. 201110145218.2 titled “DYNAMIC BALANCE MEASUREMENT METHOD AND DEVICE AND CT MACHINE HAVING THE SAME”, weight counterbalance is performed in an axial direction of the CT machine based on measurements of dynamic balance.
Therefore, in the conventional technology, before performing weight counterbalance, additional devices other than the CT machine are generally required to obtain imbalance information of the CT machine. Due to the additional devices, the structure of the CT machine is more complicated. Furthermore, additional measurement and transmission steps are further required, which makes the procedure for balancing the CT gantry more complicated.
Thus, the technical problem to be solved by those skilled in the art is to design a method and a device for balancing the CT gantry, which may perform weight counterbalance based on imbalance information obtained without adding an additional device.